The present invention relates generally to surgical instruments for implanting a new prosthesis at a joint, and for efficiently using bone graft to facilitate the implantation of a prosthesis.
It is known to use bone graft to prepare a seat for a prosthesis, either with or without a cement mantle. A bone grafting procedure is often used where there is an appreciable loss of strong bone stock, as is often the case in revision surgery (in which a previously implanted prosthesis is replaced with a new prosthesis). The seat prepared with bone graft may be made up entirely of bone graft to substantially surround a prosthesis, or the seat may be made up of bone graft and the natural bone at the implantation site (for instance, where bone graft is used to fill a relatively small void in the natural bone where the bone is otherwise intact). Bone graft typically includes crushed bone (cancellous and cortical), or a combination of these (and/or other natural materials) and synthetic biocompatible materials. Bone graft of this type is intended to stimulate growth of healthy bone. As used herein, "bone graft" shall mean materials made up entirely of natural materials, entirely of synthetic biocompatible materials, or any combination of these materials.
U.S. Pat. No. 5,015,256 to Bruce discloses a surgical technique by which the medullary canal is reamed and filled with bone graft, the bone graft being compacted by driving the stem of the prosthesis into the medullary canal. Also, U.S. Pat. No. 4,800,875 to Ray discloses a method of inserting bone graft into a bone and tamping the bone graft. European Patent Publication No. 0 179 626 A2 discloses the use of bone graft to enhance implant/bone contact, whereby the stem of a hip implant is intended to subside within an implant sleeve. Also, an article entitled "Histology Of Cancellous Impaction Grafting In The Femur," by Ling et al., Journal of Bone and Joint Surgery [Br], Vol. 75-B, No. Sep. 5, 1993, reports a 1988 revision of a hip implant in which allograft chips were impacted within the medullary canal with an oversized stem, followed by use of cement and implantation of a polished-surface stem. In addition, Complications Of Total Hip Arthoplasty, by Richard H. Rothman and William J. Hozack, W. B. Saunders Co., 1988, teaches a technique of bone grafting in the femoral canal in a revision surgery, using uncemented components.
Of course, it is desirable to properly prepare the medullary canal adjacent a joint for receiving bone graft so that a prosthesis can be properly positioned during implantation. Thus, the preparation of the medullary canal and the positioning of the prosthesis or trial prosthesis in the prepared medullary canal are often critical steps in properly implanting a prosthesis. To this end, rasps having a configuration similar to the prosthesis are well-known, as shown, for example, in U.S. Pat. No. 3,874,003 to Moser (FIG. 8), U.S. Pat. No. 4,306,550 to Forte and U.S. Pat. No. 4,552,136 to Kenna. These devices facilitate the proper shaping of the femoral medullary canal in a configuration which is similar to their respective hip prostheses or trial hip prostheses.
Centering devices (rods and guidewires) are also known for controlling the machining or other preparation of the medullary canal, as well as for centering a trial prosthesis during trial reduction or centering a prosthesis during implantation. U.S. Pat. No. 4,919,673 to Willert, U.S. Pat. No. 4,994,085 to Sawai and U.S. Pat. No. 5,078,746 to Garner each disclose the use of centering rods in the distal femoral canal to center hip joint prostheses and/or trial hip joint prostheses during trial reduction and final implantation. The hip joint prostheses and trial hip joint prostheses each have longitudinal passageways which receive the centering rods or guidewires already in the canal. Centering rods or guidewires are also used in connection with machining and shaping instruments so that the preparation of the canal is controlled about the centering rod or guidewire and so that the preparation is consistent from instrument to instrument. U.S. Pat. No. 4,341,206 to Perrett, U.S. Pat. No. 4,751,922 to DiPietropolo, U.S. Pat. No. 5,192,283 to Ling, U.S. Pat. No. 5,122,134 to Borzone and U.S. Pat. No. 5,190,548 to Davis disclose cannulated reamers and drills which are used with centering rods or guidewires for centering or positioning the shaping tools during preparation of a medullary canal or bone.
U.S. Pat. No. 5,192,283 to Ling also discloses the use of a trial hip prosthesis having a longitudinal passageway for receiving the very guidewire which facilitated the reaming and rasping of the canal. Bone graft is inserted into the canal around the guidewire, and the cannulated trial prosthesis is used to simultaneously compact and form or shape a prosthesis-receiving cavity larger than and similar in shape to the new prosthesis. Bone graft is continuously placed into the canal during the use of the cannulated trial prosthesis in order to build up the bone graft in the canal. A series of successively larger cannulated trial prostheses could be used to compact the bone graft.
The technique described in Ling is a somewhat time-consuming surgical procedure. Factors which add to the time-consuming nature of this technique include the steps which must be repeated to complete the insertion of bone graft into the canal and the requirement that all steps take place in the medullary canal. In addition, the technique described in Ling relies on a guidewire which could shift during preparation of the canal.
The present invention provides an easily implemented and efficient technique for the delivery of bone graft to a medullary canal or elsewhere in the body. One embodiment relates specifically to bone grafting within the medullary canal adjacent a joint to prepare the canal for receiving a prosthesis.